"Missing trait item" but the item has a default value

[RalfJung]

To reproduce, check out Miri at commit f2f8b98bd12e4fd6ad1d9ec1a58b80216fab2ecb. Run ./miri toolchain to install a toolchain that can build Miri, then open Miri in RA. There's an error in src/machine.rs:

not all trait items implemented, missing: `const POST_MONO_CHECKS`

The error is wrong, since this constant has a default value.

rust-analyzer version: rust-analyzer version: 0.3.1740-standalone

rustc version: rustc 1.76.0-nightly (0ff861096 2023-11-21)

relevant settings:

// Place your settings in this file to overwrite default and user settings.
{
    "rust-analyzer.rustc.source": "discover",
    "rust-analyzer.linkedProjects": [
        "Cargo.toml",
        "cargo-miri/Cargo.toml",
        "miri-script/Cargo.toml",
    ],
    "rust-analyzer.check.overrideCommand": [
        "env",
        "MIRI_AUTO_OPS=no",
        "./miri",
        "cargo",
        "clippy",
        "--all-targets",
        "--message-format=json"
    ],
    // Contrary to what the name suggests, this also affects proc macros.
    "rust-analyzer.cargo.buildScripts.overrideCommand": [
        "env",
        "MIRI_AUTO_OPS=no",
        "./miri",
        "cargo",
        "check",
        "--message-format=json"
    ],
    //
    "rust-analyzer.showUnlinkedFileNotification": false,
}

[lnicola]

That's #15909, you can use the pre-release version to get a fix.